Traveling wave electron discharge device



April 9, 1957 J. H. BRYANT ET AL 2,788,465

TRAVELING WAVE ELECTRON DISCHARGE DEVICE INVENTORS JOHN H BRYAN T TgODORE d. MARC/155E ATTORN EY April 9, 1957 J. H. BRYANT ET AL 2,788,465

TRAVELING WAVE ELECTRON DISCHARGE DEVICE Filed A rille, 1951 2 Sheets-Sheet 2 INVENTORS JOHN H. BRYANT THEODORE u. MAECHESE A wdRi f7 United States Patent TRAVELING WAVE ELECTRON DISCHARGE DEVICE John H. Bryant and Theodore J. Marchese, Nutley, N. 3:, assignors to International Telephone and Telegraph Corporation, a corporation of Maryland Application April 19, 1951, Serial No. 221,862

34 Claims. (Cl. 315--3.5)

This invention relates to traveling wave electron discharge devices and more particularly to the traveling wave amplifier type.

The traveling wave type of tube is particularly useful in wide band microwave systems since it is capable of amplifying radio frequency energy over a very wide band of frequencies. The tube includes a form of transmission line, usually a helix, for transmission of microwave energy for interaction with an electron beam closely associated with the line. The helical characteristic of the transmission line is such that the axial velocity of microwave signals conducted along the helical path is approximately the same as or slightly slower than the velocity of the electrons of the beam, whereby the electric field of the microwave signals interacts with the electron beam for amplification of the microwave signals.

Traveling wave amplifier tubes heretofore proposed usually have an electron gun and a long slender glassenclosed radio frequency section wherein the interaction occurs. The radio frequency section includes an input connection for the radio frequency energy at or immediately adjacent the output of the gun and an output connection at the other end of the section adjacent an electron collector electrode. It is one of the objects of the present invention to provide a more compact traveling wave tube with the terminals for the electrodes of the gun unit at one end of the tube, and the terminals for the radio frequency input and output connections at the other end of the tube.

Another object of the invention is to provide an electron discharge device having a housing with an electron gun unit at one end and a radio frequency transmission line conductor couplin unit at the other end, the housing and units cooperating to align the electron path in close interacting relationship with respect to the conductor of the radio frequency transmission line.

Another object of the invention is to provide a traveling wave electron discharge device having an electron gun unit and a radio frequency transmission line coupling unit with magnetic alignment members adapted to provide in elfect magnetic poles at opposite ends of the interaction path between the beam of electrons of the gun unit and the R. F. transmission line of the coupling unit.

Still another object of the invention is to provide in such devices means for proper transformer matching between the radio frequency input and output terminal connections and the conductor of the radio frequency transmission line of the tube.

One of the main features of the invention is the structural arrangement of the envelope housing and the alignment means of the electron gun unit and the R. F. coupling unit. The housing is provided with abutments which cooperate with alignment members of the electron gun unit and the R. F. coupling unit to properly position the two units with respect to each other so that the electron beam and the transmission line section of the coupling unit are disposed in substantial coaxial relationship. An abutment is also provided On the housing which provides for the proper positioning of magnetic means, such as an electroice magnetic coil, whereby the magnetic field produced thereby is coaxial of the transmission line of the tube. While the alignment members of the two units may be nonferromagnetic they preferably are of magnetic material so that they form the end paths or poles for the magnetic flux, thereby concentrating the magnetic field along the transmissions line, and also shielding the electrodes of the electron gun unit.

A feature of each of the units is the means for sealing the units to the housing. In one embodiment, each unit is provided with a similarly shaped diaphragm whereby one edge portion of each diaphragm is sealed to the housing while the other portion is sealed with the terminals or the terminal supporting member of the unit. The diaphragm provides a flexible connection for the associated unit so that atmospheric pressure acting upon the dia phragm may serve to maintain the alignment members properly seated.

Another important feature of the invention is the construction of the electron gun unit whereby an end plate supports the electrodes of the gun in proper alignment with an aperture contained in the plate. in this construction the anode of the gun is brazed to the plate so that the plate acts as a heat conductor for the anode.

Still another feature of the invention is the construction of the R. F. coupling unit which contains inlet and outlet terminal connections for R. F. energy and means for supporting a helical transmission line in axial alignment with an electron collector contained in the unit, the supporting means including extensions of the R. F. input and output connections. the alignment member of the unit when properly received in the housing positions the helical transmission line in proper position for interaction with the beam of electrons produced by the electron gun unit at the opposite end of the housing.

Still another important feature of the invention is the matching transformer sections at the opposite ends of the helical transmission line whereby connections are made with the R. F. input and output terminals. in one form a transition section comprises a tubular member containing a helically disposed slot whose pitch is varied progressively from infinity to the uniform pitch of the helical transmission line. In another form of the invention, the matching transformer comprises a coaxial section and the associated helical line has a cylindrical end conductor which is capacitively coupled to the inner conductor of the coaxial section.

The above-mentioned and other features and objects of this invention and the manner of attaining them will become more apparent and the invention itself will be best understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein:

Fig. 1 is a View in perspective of the traveling wave tube in accordance with the principles of this invention;

Fig. 2 is a longitudinal crosssectional view of the traveling wave tube shown in Fig. 1;

Fig. 3 is an enlarged cross-sectional view taken substantially along line 3-3 of Fig. 2;

Fig. 4 is a longitudinal cross-sectional view of the traveling wave tube showing a modified form of the invention;

Fig. 5 is a cross-sectional view taken substantially along line coupling unit 3. The housing has mounted thereon a magnetic unit 4 shown to be an electromagnetic coil. This unit, however, may comprise a permanent magnet instead of a coil. To properly position the magnetic unit the outer surface of the housing is provided with an abutment or shoulder 5 against which the end of the magnetic unit is positioned. Each of the two units 2 and 3 are provided with alignment members in the forms of plates 6 and 7, respectively. The housing 1 is provided with spaced abutments 8 and 9 on the inner surface thereof against which the alignment plates 6 and 7 are positioned.

Referring more particularly to the electron gun unit 2, the plate 6 is shown to contain an aperture 10 through which electrons stream from a cathode 11. The cathode together with a focusing electrode 12 are supported on rods 13 of quartz or other insulating material, which in turn are supported on an anode cylinder 14. The anode cylinder 14- includes a shaped anode 1S which together with shell 14 are brazed to the plate 6. The plate 6 thus containing the anode as an integral part thereof acts as a heat radiator therefor. To seal the electron gun unit within the housing 1 a cup-shaped diaphragm 16 is provided which contains a plurality of scaled connections for the leads of the electrodes, such as indicated by ceramic beads 17, i3 and tubular connection 19, preferably of nickel-iron alloy, for the lead 2% of the focusing electrode 12. The head 18 is sealed to the tube 19 which in turn is sealed to the diaphragm 16. The bead 17 may be sealed to the tube 19 but so long as an adequate seal is made for head 13, the bead 17 acts mainly as a lead support rather than a seal. Supported on the cup-shaped diaphragm 16 is a terminal base 21 which contains a plurality of terminals similar to the terminal 22. Centrally of the diaphragm is an exhaust tube 23 which is sealed during the exhausting operation of the tube. The terminal base 21 is secured to post 24 by any suitable means such as screws 25. The outer rim 26 of the diaphragm engages the inner surface of the housing 1 and is brazed thereto as indicated at 27.

Forhandling and during assembly operations the dia phragm 16 is secured by tie rods 28 to the alignment plate 6. When the unit is to be placed within the housing 1 the nut 29 is retracted slightly so that the alignment plate 6 to which the electrodes of the gun are secured may automatically adjust itself into position against the abutment 8'. Thus during assembly by placing the unit against the abutment 8 and brazing the diaphragm at 27 the electron gun unit is properly positioned and aligned within the housing 1.

Referring to the radio frequency coupling unit 3, the unit is shown to have an alignment plate 7 to which is secured an annular diaphragm 3t). Mounted on the plate. 7 within the diaphragm 35 are input connection 31, output connection 32 and an electron collector terminal 33. The input connection comprises a coaxial line having an outer conductor 34 and an inner conductor 35, the connection being closed by a ceramic bead 36 sealed between the outer and inner conductors 34 and 35. The output connection 32 likewise comprises a coaxial structure having an outer conductor 37 and an inner conductor 33 sealed by a head 39.

Mounted on the inner side of plate 7 is a radio frequency transmission line preferably inv the form of a helix 40. If desired this transmission linev may assume other configurations. such as a lurality of annular discs or plates, whereby the axial velocity of the radio frequency energy is made preferably slightly slower than the velocity of the beam of electrons projected from the unit 2. The helical transmission line at) is preferably supported within a quaitz tubing 41 which as shown in Fig- 2 has its ends supported in inner conductor sleeves 42 and 43 of matching transformers 44 and 45. The tubing is coated pref-- erably on its outer surface for substantially the first half of its length with lossy material 41a such as aquadag I 4 to minimize reverse R. F. conduction along the conductor 4t) and the electric field thereof.

The innermost matching transformer 44 is supported on an extension 46 of the input connection 31. The inner end of extension 46 is provided with a right angle connection 47 wherein the outer and inner conductors 34 and are brought at right angles to the transformer 44. The transformer includes the inner sleeve 42 and an outer sleeve or cylinder 43. The outer conductor 34 is connected by extension 47 to an opening in the wall of the cylinder 48 and the inner conductor 35 is connected to the sleeve 42. The end of the transformer cylinder 48 adjacent the electron gun unit is closed by a conductive plate 49 which is connected to an end sleeve 59 to which the helix is connected. The other end 51 of cylinder 38 is open. The inner conductor 35 is thus coupled by the capacity between sleeves 42 and 59.

The matching transformer at the output end of the helix it) is of the same structural arrangement as the transformer 44 comprising inner sleeve 43 to which the inner conductor 38 of the output connection 32 is connected and an outer cylinder 52 to which the outer condoctor 7 is connected. The helix ill is likewise provided with a coupling sleeve 53 which is capacitively coupled to the sleeve 43. The end of the cylinder 52 is connected to the sleeve 53 by conductive plate 54. The plate 54 and cylinder 52 are secured to the alignment plate '7.

The collector electrode 33 is supported on the plate 7 in axial alignment with aperture 55 by nickel-iron tubes 56 and 57 which are in turn connected by a ceramic sleeve 58 of matching expansion coefficient.

The entire radio frequency coupling unit 3 including the matching transformer i4, 45 and the helical transmission line 40 are assembled in a jig so that the axis of the helical transmission line is supported in proper alignment with the aperture 55. While the transmission line extends outwardly from the plate 7 there is some possibility of a cantilever action and in order to avoid this action from varying the alignment of the helical line with respect to the path of the electron beam the plate 6 of the electron gun unit is provided with a plurality of openings 59 to receive alignment pins 6t? contained on the plate 49. When the coupling unit is properly positioned with the plate against the abutment 9 the annular diaphragm 30 is brazed to the housing 1 as indicated at 61. The coupling units thus provide, at the end of the housing, input and output connections for the radio frequency energy and also a coupling terminal for the collector electrode 33.

From the foregoing it will be readily apparent that we have provided a compact traveling wave tube enclosed in a. sealed envelope in which one end is provided with a terminal base for the electrodes of the electron. gun unit and the other end with input and output terminals for the radio frequency connections. The gun unit and the R. F. coupling unit are provided with alignment men1- bers whereby proper alignment is obtained when the units are mounted in position within the housing 1. Further, the alignment members or plates being of magnetic material provide a flux path much like magnetic poles for the magnetic unit 4 whereby maximum flux density is produced axially of the helical transmission line thus insuring a pencil-like beam throughout the length of the helix. in some tube structures the alignment members may not be of ferromagnetic material, particularly where the members are needed for structural support rather than as magnetic barriers or flux paths.

Referring to Figs. 4 and 5, a fragmentary showing of another tube disclosing a modified form of this inven tion is illustrated. Where the elements of the tube are identical with those of the embodiment shown inFigs. l, 2-and 3, the same reference characters are used. The differences in the embodiment of Figs. 4 and 5 are in the supporting arrangement for the helical transmission line, the matching transformers, the coupling arrangements between the transmission line and the input and output connections greener 31 and 32 and the housing mounting arrangements of l the gun and R. F. coupling units.

The input terminal connection 31 has an extension 46 as previously described except for the inner conductor 35. The inner conductor 35 is provided with a matching transformer or transition section 62. This section 62 includes a plurality of turns 63, the pitch of which increases from that of the helix 64 to infinity at the point 65 Where the section is coupled to the conductor 35. The helix at the end 64 is connected by a right angle bend 66 to a helix section 67 which in turn is connected by a right angle bend 63 to the helix 64. The outer conductor 34 is terminated in the neighborhood of the right angle connection 66.

The output of the helix 64 is likewise connected at a right angle to a helix section 69 which in turn is connected to a matching transformer section 70 to the inner conductor 33 of the output terminal 32. The outer conductor 37 of the terminal 32 is terminated in the neighborhood of the connection between helix section 69 and the transformer section 70.

To properly support the transmission helix 64 in alignment with the apertures and 55 through which the electron beam fiows, two supports 71 and 72 carried by the extension 46 are provided. As shown in Figs. 4 and 5, these two supports are identical. Each support includes an eyelet or sleeve 73 which has a flange 74 to which are spot welded pins 75 and 76, which in turn support opposed clamps 77 and 78. The clamp 77 rests on a pair of stop pins 79 and 8t) welded or otherwise secured to the pins 75 and 76. The two clamps 77 and '78 are provided with V-shaped notches which fit over the quartz tubing 81. To provide some resilience in the support the upper clamp 78 is engaged by spring 82 which are retained on the upper ends of the pins 75 and 76 by stop pins 83.

The radio frequency energy received over the coaxial input terminal connection 31 is transferred to the helix 67 by means of the transformation section 62. The R. F. energy is conducted by the helical section 67 to the helix 64 Where the electric field of the R. F. energy interacts with the electrons of the electron beam flowing axially of the helix. Since the axial velocity of the radio frequency energy is slightly less than the velocity of the electrons, a transfer of energy from the electron stream to the waves of the radio frequency energy will be effected. This will result in the amplification of the radio frequency energy which is transferred through section 70 to the output coaxial terminal 32.

In the embodiment of Fig. 4 the mounting arrangements of the electron gun unit and the R. F. coupling unit are different from that shown in the embodiment of Fig. 2. The housing In is provided with an abutment in the form of a recess 84 against which .a lateral circumferential flange 85 of the end plate 7a is received for alignment purposes. In this position the flange 85 is brazed to the housing as indicated at 86. At the other end of the housing la an annular ring 87 of magnetic material is received in a recess 88 where it is brazed to the housing 1a. The ring 87, which in efizect forms an extension of the housing 1a, is provided with an annular abutment 89 against which the alignment plate 6a is adapted to be positioned. A cylindrical housing 90 is brazed to the ring 87 and in etfect forms an extension of the housing 1a and an abutment for the magnetic device 4. When the gun unit 2a is introduced into the end of the housing its innermost position is determined by the abutment 89 against which the plate 6a is positioned. The gun in this position is secured by brazing the end diaphragm to the housing 90 as previously de scribed in connection with the embodiment of Fig. 2.

At the other end of the housing in the alignment plate 7a is sealed to the inlet and outlet connecting terminals 31 and 32 and in effect terminates the housing.

In this embodiment of the invention a complete magnetic path is provided between the end pieces 91 and 92 of the magnetic device 4. The magnetic flux thus has a direct path from the magnetic device 4 to the alignment plate 6a and 7a whereby the magnetic field is concentrated axially of the housing between plates 6a and 7a.

In Fig. 6 a further modification of the alignment plate is provided. The alignment plate 6b is: provided with a peripheral flange extending axially of the plate as indicated at 93 and 94. In this embodiment the gun unit including the housing b may be completely assembled on the plate 61; prior to its application to housing 1a. The gun unit thus assembled can be mounted and brazed onto the housing 1:: against the abutment 88.

While we have described above the principles of our invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of our invention, as set forth in the objects thereof and in the accompanying claims.

We claim:

1. A traveling wave electron discharge device comprising a gas-tight enclosure including a housing, an electron beam forming unit disposed at one end of said housing to project an electron beam along a given rectilinear path in said housing, elongated conductive means disposed with its principal longitudinal axis parallel to and adjacent said path for transmission of radio frequency energy in interacting relation with the electrons of said beam, and a radio frequency coupling unit disposed at the other end of said housing, said coupling unit having separate input and output terminal connections for said conductive means entering said gas-tight enclosure at said other end of the housing.

2. A traveling Wave electron discharge device comprising a housing, an electron beam forming unit disposed at one end of said housing to project an electron beam along a given rectilinear path in said housing, elongated conductive means disposed with its principal longitudinal axis parallel to and adjacent said path for transmission of radio frequency energy in interacting relation with the electrons of said beam, and a radio frequency coupling unit disposed at the other end of said housing, said coupling unit having separate input and output terminal connections for said conductive means, said coupling unit including means for supporting said conductive means.

3. A traveling Wave electron discharge device comprising a housing, an electron beam forming unit disposed at one end of said housing to project an electron beam along a given rectilinear path in said housing, elongated conductive means disposed with its principal longitudinal axis parallel to and adjacent said path for transmission of radio frequency energy in interacting relation with the electrons of said beam, and a radio frequency coupling unit disposed at the other end of said housing, said coupling unit having separate input and output terminal connections for said conductive means, said housing being provided with two spaced abutments projecting therefrom and said electron beam forming unit including alignment means adapted to be positioned against one of said abutments and said radio frequency coupling unit including alignment means adapted to be positioned against the other of said abutments.

4. A traveling wave electron discharge device according to claim 3, wherein the housing has a third abutment projecting therefrom at a fixed distance with respect to one of the aforementioned abutmcnts, said device further including a magnetic field forming unit positioned on said housing in a position determined by said third abutment to provide a magnetic field along said given path.

5. A traveling wave electron discharge device according to claim 3, further including a pair of positioning plates, the two mentioned alignment means each including one positioning plate positioned within said housing for its respective unit, the plates each being positioned within said housing against one of the two spaced abutments.

6. A traveling wave electron discharge device comprising ahousing, an electron beam forming unit disposed at one end of said housing to projectan electron beam along a given rectilinear path in said housing, elongated conductive means disposed with its principal longitudinal axis parallel to and adjacent said path for transmission of radio frequency energy in interacting relation with the electrons of said beam, and a radio frequency coupling unit disposed at the other end of said housing, said coupling unit having separate input and output terminal connections for said conductive means, the electron beam forming unit and the radio frequency coupling unit each including a member of magnetic material disposed adjacent said given path and a magnetic field forming device disposed with the pole pieces thereof in magnetic coupling relation with said members.

7. A traveling wave electron discharge device comprising a housing, an electron beam forming unit disposed at one end of said housing to project an electron beam along a given rectilinear path in said housing, elongated conductive means disposed with its principal longitudinal axis parallel to and adjacent said path for transmission of radio frequency energ; in interacting relation with the electrons of said beam, and a radio frequency coupling unit disposed at the other end of said housing, said coupling unit having separate input and output terminal connections for said conductive means, the electron beam forming unit including a plurality of axially aligned electrodes for producing said electron beam, said device further including an alignment member mounted in a given position in said housing to position said electrodes for directing said beam axially of said housing.

8. A traveling wave electron discharge device according to claim 7, wherein the alignment member comprises a plate having an aperture theretl rough and means for supporting said electrodes on said plate in axial alignment with said aperture.

9. A traveling wave electron discharge device according to claim 8, wherein one of the electrodes is an anode disposed'contiguous to said plate whereby said plate acts as a heat conductor for said anode.

10. A traveling wave electron discharge device accord ing to claim 8, further including means to provide a magnetic field axially of said electron beam, and said plate is of magnetic material disposed adjacent one end of said magnetic field forming means, thus forming a part of the path for the magnetic flux of said magnetic field forming means and thereby shielding said electrodes from said magnetic flux.

11. A traveling wave electron discharge device comprising a housing, an electron beam forming unit disposed at one end of said housing to project an electron beam along a given rectilinear path in said housing, elongated conductive means disposed with its principal longitudinal axis parallel to and adjacent said path for transmission of radio frequency energy in interacting relation with the electrons of said beam, and a radio frequency coupling unit disposed at the other end of said housing, said coupling unit having separate input and output terminal connections for said conductive means, the electron beam forming unit including an alignment member and a sealing diaphragm mounted thereon at spaced points, said housing having means to limit the inward positioning of said member and means sealing said diaphragm to said housing.

12. A traveling Wave electron discharge device according to claim ll, wherein said electron beam forming unit includes electrodes for producing said electron beam, said electrodes being mounted between said alignment member and said diaphragm, and terminals for said electrodes carried by said diaphragm.

13. A traveling wave electron discharge device according to claim 12, wherein said diaphragm is cup-shaped and has an end wall portion, said device further including a terminal base for said terminals carried by said end wall portion of the cup shaped diaphragm.

14. A traveling Wave electron discharge device comprising a housing, an electron beam forming unit disposed at one end of said housing to project an electron beam along a given rectilinear path in said housing, elongated conductive means disposed with its principal longitudinal axis parallel to and adjacent said path for transmission of radio frequency energy in interacting relation with the electrons said beam, and a radio frequency coupling unit disposed at the other end of said housing, said coupling unit having separate input and output terminal connections for said conductive means, the housing having an abutm nt and the radio frequency coupling unit includan alignment member mounted thereon and positioned in said housing against said abutment with the input and output terminal connections thereof carried by said mcmber.

15. A traveling wave electron discharge device according to claim 14, wherein said alignmen member includes a plate having an aperture therethrough for passage of said electron beam, and an electron collector electrode carried by the outer portion of said plate in alignment with said aperture.

16. A traveling Wave electron discharge device according to claim 15, wherein said radio frequency coupling unit includes an annular diaphrgam carried by said plate, said diaphragm being adapted to be sealed to said housing along a portion thereof spaced from said plate.

17. A traveling wave electron discharge device according to claim 14, wherein the input terminal connection of the radio frequency coupling unit is in the form of a coaxial conductor, which extends through said alignment member to adjacent said electron beam forming unit and a transformer matching section is coupled between said input coaxial conductor and said radio frequency conductive means.

I8. A traveling wave electron discharge device according to claim 17, wherein the transformer matching section includes a coaxial structure with the center conduc; tor thereof in tubular form coupled electrically to said radio frequency conductive means and the outer conductor thereof being in the form of a conductive cylinder, means electrically connecting one end of said cylinder to said radio frequency conductive means, and means connecting the center and outer conductors of said input coaxial connection to the corresponding inner and outer conductors of said transformer matching section.

19. A traveling wave electron discharge device according to claim 18, wherein said radio frequency conductive means is a helical conductor having cylinder portions at the ends thereof.

20. A traveling wave electron discharge device according to claim 17, wherein the radio frequency conductive means is a helical conductor and the matching transformer section includes a helical portion connected coaxially to the center conductor of one of the coaxial connections, said. helical portion having a pitch which varies progressively from the pitch of said helix at one end to infinity at its other end.

-2l. A traveling wave electron discharge device according to claim 14, wherein the radio frequency conductive means is a helical conductor, insulating tubing supporting said helical conductor axially thereof and means supporting said tubing, at least in part, from the radio frequency input connection carried by said radio frequency coupling unit.

22. A traveling wave electron discharge device according to claim 14, wherein said radio frequency coupling unit further includes an annular diaphragm carried by said alignment member and means sealing said diaphragm to said housing along a line spaced from said member.

23. In a traveling wave electron discharge device, an electron beam forming unit comprising an end plate having an aperture therethrough, a sealing diaphragm for hermetically sealing one end of said housing, means supporting said diaphragm in spaced relation to said plate, electrodes mounted "between said diaphragm and said plate in coaxial alignment with said aperture, and terminals for said electrodes carried by said diaphragm.

24. In a traveling wave electron discharge device according to claim 23, wherein the diaphragm is cupshaped and includes a terminal base for said terminals carried by the end wall portion of the cup-shaped diaphragm.

25. In a traveling wave electron discharge device according to claim 23, wherein one of the electrodes is an anode carried contiguous to said end plate whereby the end plate acts as a heat conductor for said anode.

26. In a traveling wave electron discharge device, an elongated housing, a radio frequency coupling unit comprising an alignment member receivable in one end of said housing to position said unit in a predetermined location therein, a radio frequency conductive element disposed in said housing lengthwise thereof, input and output radio frequency connection leads carried by said member, and transformer matching means coupling said radio frequency conductive element to said input and output connection leads.

27. In a traveling Wave electron discharge device according to claim 26, wherein the radio frequency input and output connections are each in the form of a coaxial connection, and the transformer matching means includes a coaxial structure wherein the center conductor thereof is in tubular form coupled electrically to said radio frequency conductive element and the outer conductor thereof is in the form of a conductive cylinder connected electrically at one end to said radio frequency conductive element, and means connecting the center and outer conductors of said input coaxial connection to the corresponding inner and outer conductors of said transformer matching means.

28. In a traveling wave electron discharge device according to claim 26, wherein said radio frequency conductive element is a helical conductor, the input and output connection leads are each in the form of a coaxial connection, and the transformer matching means in cludes a helical portion connected coaxially to the center conductor of one of the coaxial connections, said helical portion having a pitch which varies progressively from the pitch of said helical conductor at one end to infinity at its other end.

29. In a traveling wave electron discharge device according to claim 26, wherein the radio frequency conductive element is a helical conductor, an insulating tubing for supporting said helical conductor, and means supporting said tubing from the radio frequency input and output connections carried by said radio frequency coupling unit.

30. A traveling wave electron discharge device comprising an elongated housing containing an electron beam forming gun at one end, a helical conductor for radio frequency energy disposed along the beam for interaction with the electrons from said gun, terminal connections disposed at the gun end of said housing in electrical connection with the electrodes of said gun, radio frequency input and output terminal connections disposed at the other end of said housing and means coupling said input and output terminals to opposite end portions, respectively of said helical conductor.

31. in a traveling wave electron discharge device, a magnetic field forming device having spaced end pieces, said end pieces having aligned openings extending axially therethrough, said magnetic field forming device being adapted to provide a magnetic field along the axis of said openings, an electron gun unit having an alignment member which supports electrodes for producing an electron beam along a given path, a radio frequency transmission line coupling unit having an alignment member supporting a transmission line conductor for positioning adjacent the path of the electron beam of said gun unit, and means assembling said units with the alignment member of said gun unit disposed concentrically of the opening of one of said end pieces and the alignment .member of said coupling unit disposed concentrically of the other of said end pieces whereby said path coincides substantially with the axis of said openings.

32. in a traveling wave electron discharge device according to claim 31, wherein said end pieces and said alignment members are of magnetic material.

33. In a traveling wave electron discharge device according to claim 32, wherein said members are in contact with said end pieces and form in effect oppositely disposed magnetic poles coaxially of the path of said electron beam.

34. In a traveling wave electron discharge device according to claim 32, wherein the magnetic device includes an electromagnetic coil disposed between said end pieces.

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